It is often difficult to determine when a fault occurs in a system having a shared data bus, particularly while running tests and during normal operations. Faults may be caused or triggered by messages that transfer data or send control messages to devices over such data buses. Shared data buses may be employed in systems such as Supervisory Data Acquisition (SCADA) systems and avionics systems that can operate according to one or more technical standards such as the RS-422 and MIL-STD-1553 standards.
To help solve faults in a system comprising a shared data bus, many vendors have created logging technologies that reside on the shared data bus and capture data packets being communicated via the bus. These logging technologies may miss bus glitches and packet collisions occurring on the monitored shared data bus because they decode messages before saving them, losing the raw (pre-decoded) signal information. For this and other reasons, when glitches are missed or collisions occur, these logging technologies can miss these anomalies.
Shared data bus logging systems may have other hurdles associated with logging data being continuously streamed. For example, the MIL-STD-1553 data bus has a throughput rate of 1 MHz or 1,000,000 samples per second, and it employs a differential pair that can double that rate up to 2 MHz. Each bus also may include a backup bus that doubles the total amount of data being transferred in the system again. Because of limitations in their storage capacity, some commercial data loggers limit the amount of data being collected to only valid data packets and do not capture all data being streamed. However, to adequately capture an entire MIL-STD-1553 bus signaling, a logging system may need to sample at an effective minimum rate of up to or about 8 MHz. Accordingly, the amount of data to be captured may add up to as much as 28.8 GB per hour.